7

5 days:
The half life (time to elimination of half the drug) of Doxycycline is long, 15-24 hours. The drug is not completely eliminated until 5 half lives after taking the last dose. I would wait 5 days after the last dose of Doxycycline until going in the sun and them use sun screen.
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9

See below:
Doxycycline is given both orally and intravenously. It is used to treat several different species of bacteria and several different bacterial illnesses. It covers most strains of staphylococcus aureus including mrsa, hemophilus influenza, chlamydophilia, mycoplasma and some strains of gram negative bacteria. If you are infected with a susceptible bacteria it is usually curative.
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10

100 mg twice daily :
Doxycycline is usually given in doses of 100 mg orally or IV twice daily for just about all conditions. Cholera is an exception. The type of condition that is being treated dictates the duration of therapy.
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